Few health issues have been more confusing than the barrage of news reports over the past three months linking popular pain relievers -Vioxx, Celebrex, Bextra and naproxen, the drug in Aleve - with heart attack.

Q: What is the evidence against these pain drugs?

A: The first evidence against Vioxx came in March 2000 from a study of rheumatoid arthritis patients. In it, Vioxx users had five times the risk of heart attack as naproxen users. Last September, a three-year study of patients with a genetic polyp disease showed that the patients who took Vioxx for more than 18 months were twice as likely to have heart attacks or strokes. Then, in December, another polyp study using Pfizer’s Celebrex found that Celebrex users had twice the risk of heart attack. Days later, the National Institute of Health stopped a study of 2,400 Alzheimer’s patients, citing higher risks from naproxen. Questions have also emerged about Pfizer’s Bextra.

Q: Can we conclude these painkillers are dangerous?

A: The evidence sounds compelling, but we know very little about the risk associated with these drugs, said Brooks S. Edwards, cardiologist at the Mayo Clinic in Rochester and editor in chief for Mayoclinic.com. None of these studies was specifically designed to assess cardiovascular risk.

Q: Are such serious health risks unusual for approved drugs?

A: Every day, consumers assume serious risks when they take common drugs. “The patient rightfully wants to be protected from a dangerous drug,” said Dr. Edwards, who has been an investigator for Pfizer on a Viagra study. “Patients also have to understand that there is no medication out there that is 100 percent safe and effective. Every prescription I write carries some risks.”

Q: Why would some pain drugs raise heart risk when we know that aspirin protects the heart?

A: Aspirin and other older pain killers block two enzymes - Cox-1 and Cox-2 - that are involved in inflammation and pain. The main drugs under scrutiny are Cox-2 inhibitors - that means they only block the Cox-2 enzyme. This is bad and good. It is the blocking of the Cox-1 enzyme that leads to the serious gastrointestinal bleeding that kills as many as 17,000 patients a year. But blocking Cox-1 may also lower heart attack risk.